This application incorporates by reference of Taiwan application Serial No. 90107009, filed Mar. 23, 2001.
1. Field of the Invention
The invention relates in general to a multi-resolution charge-coupled device (CCD) sensing apparatus, and more particularly to a multi-resolution charge-coupled device (CCD) sensing apparatus applied to the CCD module and the CIS (Contact Image Sensor) module.
2. Description of the Related Art
In recent years, the scanner has been widely used. The user requires choosing from scanning modes of different resolutions for scanning in accordance with the property of the document to be scanned. Conventionally, there are several ways for setting the resolution, which might be accomplished by using either software or hardware. The way by using hardware is usually direct and fast.
The scanning procedures of the scanner with the CCD module are stated as follows. The carriage in the scanner has an illumination source. After the illumination source produces the light, the light is reflected by the document to be scanned and directed back to the carriage. The light signal is processed by the optical components, such as the mirrors and lenses, and received by the CCD module. The CCD module senses the magnitude of light signal and then generates corresponding scanning image data.
Referring to FIG. 1, a CCD module using a conventional charge-coupled device (CCD) sensing device is shown. The CCD module 100 includes a CCD sensing device 102, a control circuit 104 and an output capacitor C. The CCD sensing device 102 mainly includes a photo sensor set 106, shift gate 108, and CCD shift register 110. The CCD sensing device 102 with a resolution of 1200 dpi (dots per inch) is taken for example. The photo sensor set 106 includes 1200 photo sensing components D1xcx9cD1200 for converting the light signals into the charge signals S1xcx9cS1200. The photo sensing components maybe photo diodes. The shift gate 108 is used for controlling the transmission of the charge signals S1xcx9cS1200. When the photo sensing components D1xcx9cD1200 are exposed to light for a predetermined period of time, the photo sensing components D1xcx9cD1200 generate enough amount of charges, and then the shift gate 108 is open so that the charge signals S1xcx9cS1200 are sent to the CCD components E1xcx9cE1200 in the CCD shift register 110. Subsequently, the charge signals S1xcx9cS1200 stored in the CCD components E1xcx9cE1200 are serially outputted. The control circuit 104 is used for serially storing the charge signals, which are outputted due to the control of the CCD shift register 110, in the capacitor C to acquire the analog output signal Out. The output signal Out is processed by a next stage circuit (not shown) and the scanning image data are then acquired.
However, using different scanning modes of different resolutions for a user is necessary. For example, the scanning mode of high-resolution for scanning is required if the document to be scanned is a high color image. If the document to be scanned is text, it simply requires the scanning mode of low-resolution for scanning. In FIG. 1, the CCD sensing device 102 is a high-resolution sensing device, some properties of the CCD sensing device 102 has to be discarded when it is used for scanning at a low resolution.
As shown in FIG. 1, the CCD sensing device 102 with a high resolution is used for scanning at a low resolution of 600 dpi and the operation is described as follows: after the photo sensing components D1xcx9cD1200 are exposed to light, the charge signals S1xcx9cS1200 are stored in the CCD components E1xcx9cE1200. When the charge signals S1xcx9cS1200 are outputted, the control circuit 104 will store 600 charge signals, such as S2, S4, S6 . . . S1200, in the capacitor C in order to acquire the scanning image data of 600 dpi. Although the scanning image data are of low resolution, the time for shifting out the electric charges stored in the CCD components to the capacitor C is still the same as before and does not decrease any. Therefore, for the conventional CCD sensing device 102, scanning at a low resolution does not enhance the scanning speed and takes the same time with scanning at a high resolution.
The chips for the CCD sensing device with different resolutions have been widely used in the marketplace. To solve the above-mentioned problem, the CCD module having multiple CCD sensing devices with several different resolutions becomes available in the market.
Referring to FIG. 2, the conventional CCD module having multiple CCD sensing devices is shown. The CCD module 200 having three CCD sensing devices is an example for further illustration. The CCD module 200 has a CCD sensing device 202a with a resolution of 1200 dpi, a CCD sensing device 202b with a resolution of 600 dpi, and a CCD sensing device 202c with a resolution of 300 dpi. The CCD sensing devices 202a, 202b, and 202c have 1200 photo sensing components Da1xcx9cDa1200, 600 photo sensing components Db1xcx9cDb600, and 300 photo sensing components Dc1xcx9cDc300 respectively. The CCD shift registers 210a, 210b, and 210c in the CCD sensing devices 202a, 202b, and 202c are respectively controlled by the pulse signals CK1, CK2, and CK3 and have 1200 CCD components Ea1xcx9cEa1200, 600 CCD components Eb1xcx9cEb600, and 300 CCD components Ec1xcx9cEc300 respectively. The shift gates 208a, 208b, and 208c respectively control the transmission of the charge signals of the CCD sensing devices 202a, 202b, and 202c. 
When the user chooses different scanning modes of different resolutions for scanning, the control circuit 204 will choose the outputs of the corresponding CCD sensing devices 202a, 202b, and 202c and send them to the capacitor C. That is to say, while scanning, the photo sensor sets 206a, 206b, and 206c are simultaneously exposed to light and store the charge signals in the CCD shift registers 210a, 210b, and 210c. When choosing the scanning mode of 1200 dpi, the control circuit 204 chooses the output of the CCD shift registers 210b or 210c. Since the CCD components of the CCD shift registers 210b and 210c are both far less than that of CCD shift registers 210a, the time to shift out the stored charges is far less in the CCD components Eb1xcx9cEb600 or Ec1xcx9cEc300 than in the CCD components Ea1xcx9cEa1200. Therefore, using the CCD module in FIG. 2 while scanning at a low resolution will enhance the scanning speed.
Even so, using the CCD module 200 in FIG. 2 will confront the following disadvantageous situations. The conventional CCD module 200 uses the chip consisting of three juxtaposed CCD sensing devices with different resolutions. Failure to precisely focus might be caused during exposure to light. The photo sensor sets 206a, 206b, and 206c are parallel with one another and simultaneously receive the exposures of the light signals from the same optical components. If the optical components are set to focus on the photo sensor set 206a, scanning at a low resolution might cause failure to precisely focus and the scanning quality might be seriously influenced. Besides, it is necessary to use three different CCD sensing devices belonging to three chips. The required size is very large and the cost is quite high.
It is therefore an object of the invention to provide a multi-resolution charge-coupled device (CCD) sensing apparatus, used for scanning at different resolutions. The multi-resolution CCD sensing apparatus along with a photo sensor set and several CCD shift registers achieve the economy in size, low cost, and high yield rate. It speeds the scanning at a low resolution without causing failure to focus and therefore enhances the image scanning quality.
The invention achieves the above-identified objects by providing a multi-resolution charge-coupled device (CCD) sensing apparatus, comprising a photo sensor set, a shift gate, and at least one first CCD shift register and one second CCD shift register. The photo sensor set includes several photo sensing components for receiving light signals and generating a plurality of corresponding charge signals accordingly. The shift gate includes several switches for receiving the charge signals from the photo sensing components. The first CCD shift register includes M CCD components while the second CCD shift register includes N CCD components. The M CCD components are coupled with parts of the switches and the N CCD components are coupled with parts of the switches, wherein M and N are positive integers and M is larger than N, value M corresponds to scanning at a first resolution, and the value N corresponds to scanning at a second resolution. The switches selectively output the charge signals to the M CCD components while scanning at the first resolution, and the switches selectively output the charge signals to the N CCD components while scanning at the second resolution.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.